Portable fan



FIG. 1 is a front elevational view of a portable fan showing our new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is a left side elevational view thereof, the right side being substantially identical except for the control knob. 

The ornamental design for a portable fan, as shown and described. 